Main landing gears may be installed in an aircraft during or after final body join. Each main landing gear may be mounted to spars or other primary structural members of a wing.
Consider the example of a large commercial jetliner in which each main landing gear weighs tens of thousands of pounds and, when upright, exceeds aircraft working height. Clearances for moving the main landing gear through an opening in the wing's skin, and positioning the main landing gear at a mounting location at a spar, are very tight. If the main landing gear bumps into the skin or spar, it can damage the skin or spar. The damage can be expensive in terms of money and time, especially if production is delayed.
Some aircraft factories have pits for installing main landing gears. An upright landing gear is loaded into the pit, the aircraft is moved over the pit, and the upright landing gear is raised until its load bearing interfaces arrive at their mounting locations.
If a pit is not available, a landing gear loader may be used to position a main landing gear underneath a wing, and translate and tilt the landing gear until its load bearing interfaces arrive at their mounting locations. However, this process involves a series of discrete movements. After each discrete movement, a visual inspection is performed to determine whether there is sufficient clearance. Installation time is prohibitive.